Farms and forests: evaluating the biodiversity benefits of kelp aquaculture

The biodiversity benefits of kelp aquaculture and afforestation are increasingly acclaimed as the industry continues to grow and develop globally, however, whether farmed kelp can provide this ecosystem service remains unclear. Using peer-reviewed literature, we evaluated whether kelp farms provide biodiversity benefits, and identified only 23 studies that discussed the effects of kelp aquaculture on biodiversity, half of which were broad reviews that only assessed the concept of 'biodiversity' peripherally (e.g. did not focus on specific responses or taxa). There is also a general lack of experimental research on the topic. Based on the evidence, it seems that kelp farms can create habitat via changes to the local environment, particularly through the provision of structure and changed nutrient cycling. While this can lead to increased abundance and diversity among certain taxa (e.g. fouling organisms), it seems that kelp farms typically create novel habitats that support distinct communities not equivalent to natural kelp forests. Moreover, the potential for kelp farms to support biodiversity depends on a range of operational factors, many of which may be at odds with farming objectives that require the harvest and removal of the habitat that farms provide. While more work needs to be done to address the complexity of comparisons between kelp farms and forests, especially at appropriate experimental scales, it currently seems unlikely that kelp farms will act as kelp forests and deliver meaningful biodiversity outcomes. We should instead recognise farms for providing their own valuable services and support restoration and conservation practices of kelp forests to pursue biodiversity outcomes.